I am having apple iphone 4 with 4.3.3 software update. It was working fine till yesterday but I donít know what happened. I am able to receive call and send text messages but I am not able to make outgoing calls since yesterday. Whenever I try to make any call, I get a call failed error message. My iphone 4 is actually unlocked and I am using Airtel Network (india) service. I would like to know why this thing is happening to me. Any suggestions for the same would be highly appreciated. Thank you in advance.